From 87101e7d83420a733f9d62b1926b158da921ea70 Mon Sep 17 00:00:00 2001
From: Ian Romanick <ian.d.romanick@intel.com>
Date: Fri, 1 Mar 2024 17:11:57 -0800
Subject: [PATCH] intel/compiler: Ensure load_barycentric_at_sample and
 load_interpolated_input remain together

This previously worked by luck because we were incorrectly calling
nir_opt_remove_phis before calling nir_convert_from_ssa. See also #10727.

No shader-db or fossil-db changes on any Intel platform.

v2: Handle the load_interpolated_input and load_barycentric_at_sample as
separate passes. Based on discussion with Ken starting at
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28136#note_2330424.

Fixes: 74a40cc4b6e ("intel/fs: move lower of non-uniform at_sample barycentric to NIR")
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28136>
---
 ..._lower_non_uniform_barycentric_at_sample.c | 73 ++++++++++++++++++-
 1 file changed, 71 insertions(+), 2 deletions(-)

diff --git a/src/intel/compiler/intel_nir_lower_non_uniform_barycentric_at_sample.c b/src/intel/compiler/intel_nir_lower_non_uniform_barycentric_at_sample.c
index 49fd1b44add..d2538c841e0 100644
--- a/src/intel/compiler/intel_nir_lower_non_uniform_barycentric_at_sample.c
+++ b/src/intel/compiler/intel_nir_lower_non_uniform_barycentric_at_sample.c
@@ -48,6 +48,9 @@ intel_nir_lower_non_uniform_barycentric_at_sample_instr(nir_builder *b,
        !nir_src_is_divergent(intrin->src[0]))
       return false;
 
+   if (intrin->def.parent_instr->pass_flags != 0)
+      return false;
+
    nir_def *sample_id = intrin->src[0].ssa;
 
    b->cursor = nir_instr_remove(&intrin->instr);
@@ -59,6 +62,7 @@ intel_nir_lower_non_uniform_barycentric_at_sample_instr(nir_builder *b,
       nir_push_if(b, nir_ieq(b, sample_id, first_sample_id));
       {
          nir_builder_instr_insert(b, &intrin->instr);
+         intrin->def.parent_instr->pass_flags = 1;
 
          nir_src_rewrite(&intrin->src[0], first_sample_id);
 
@@ -69,12 +73,77 @@ intel_nir_lower_non_uniform_barycentric_at_sample_instr(nir_builder *b,
    return true;
 }
 
+static bool
+intel_nir_lower_non_uniform_interpolated_input_instr(nir_builder *b,
+                                                     nir_instr *instr,
+                                                     void *cb_data)
+{
+   if (instr->type != nir_instr_type_intrinsic)
+      return false;
+
+   nir_intrinsic_instr *load_ii = nir_instr_as_intrinsic(instr);
+   if (load_ii->intrinsic != nir_intrinsic_load_interpolated_input)
+      return false;
+
+   assert(load_ii->src[0].ssa->parent_instr->type == nir_instr_type_intrinsic);
+
+   nir_intrinsic_instr *bary =
+      nir_instr_as_intrinsic(load_ii->src[0].ssa->parent_instr);
+   if (bary->intrinsic != nir_intrinsic_load_barycentric_at_sample)
+      return false;
+
+   if (nir_src_is_always_uniform(bary->src[0]) ||
+       !nir_src_is_divergent(bary->src[0]))
+      return false;
+
+   nir_def *sample_id = bary->src[0].ssa;
+
+   b->cursor = nir_instr_remove(&load_ii->instr);
+
+   nir_push_loop(b);
+   {
+      nir_def *first_sample_id = nir_read_first_invocation(b, sample_id);
+
+      nir_push_if(b, nir_ieq(b, sample_id, first_sample_id));
+      {
+         nir_def *new_bary = nir_load_barycentric_at_sample(
+            b, bary->def.bit_size, first_sample_id,
+            .interp_mode = nir_intrinsic_interp_mode(bary));
+
+         /* Set pass_flags so that the other lowering pass won't try to also
+          * lower this new load_barycentric_at_sample.
+          */
+         new_bary->parent_instr->pass_flags = 1;
+
+         nir_builder_instr_insert(b, &load_ii->instr);
+
+         nir_src_rewrite(&load_ii->src[0], new_bary);
+
+         nir_jump(b, nir_jump_break);
+      }
+   }
+
+   return true;
+}
+
 bool
 intel_nir_lower_non_uniform_barycentric_at_sample(nir_shader *nir)
 {
-   return nir_shader_instructions_pass(
+   bool progress;
+
+   nir_shader_clear_pass_flags(nir);
+
+   progress = nir_shader_instructions_pass(
+      nir,
+      intel_nir_lower_non_uniform_interpolated_input_instr,
+      nir_metadata_none,
+      NULL);
+
+   progress = nir_shader_instructions_pass(
       nir,
       intel_nir_lower_non_uniform_barycentric_at_sample_instr,
       nir_metadata_none,
-      NULL);
+      NULL) || progress;
+
+   return progress;
 }